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HoyaBear
 
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B&B Headers Leaking

Hey guys,

Well I finally got the oil issues taken care of (for the most part) so now its on to other areas... Spending so much time under the car, I noticed that there is an exhaust leak in my headers (the red highlighted area in the photo) and I am looking for ideas on how to fix it. Would it be best to have this welded up? Is there a reason it wasn't welded from B&B (I assume to ease shipping difficulties??) and is there a reason not to weld this? I'm willing to bet that I'm losing a good bit of HP from this exhaust leak and it is probably why the car doesn't build boost as quickly as I thought it should. Thanks - Jon
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'86 930: 3.4 Andial build, Web GT2 Evo cams, Carrillo rods, ported/polished heads, MSD 6530, B&B headers/exh + intercooler, K27HF, 1 bar spring, Tial wastegate, Andial FE, Lindsey Fuchs. Back in black!!!
Past:997S cab; '88 930; '86 951; C5 Vette; 4th Gen Z28; 3rd Gen Trans Am GTA; '71 Z28
Old 11-07-2009, 12:05 PM
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That is a standard slip joint, required to prevent cracking. The motor and exhaust will expand and contract with heat, the joint will take up the difference in movement. Usually these joints will seal up with time and soot, a better sealing option is is a flex joint.
Old 11-07-2009, 01:37 PM
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HoyaBear
 
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Racerabbit,

As the headers have been on the car for 10K+ miles, should they still be leaking? It is a pretty noticeable leak and it occurs when the car is both hot and cold. If this slip joint cannot be welded, what else could be used to fix the leak? I am definitely losing boost here, I have a 1 bar spring and can't get over .8 bar. Thanks
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'86 930: 3.4 Andial build, Web GT2 Evo cams, Carrillo rods, ported/polished heads, MSD 6530, B&B headers/exh + intercooler, K27HF, 1 bar spring, Tial wastegate, Andial FE, Lindsey Fuchs. Back in black!!!
Past:997S cab; '88 930; '86 951; C5 Vette; 4th Gen Z28; 3rd Gen Trans Am GTA; '71 Z28
Old 11-07-2009, 02:12 PM
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As a fabricator, I usually will use a "double slip" joint on boost applications, so if the joint can still be slipped apart, you could have a second overlapping sleeve welded on the outside (must be tight). An example of this is below (made by Burns). The other option would be to have the slip joint cut out and replaced with a stainless flex joint.



It may also be possible to disassemble the joint, and reassemble it with high temp silicone, it holds up better than you would believe, and will still allow some movement.

Last edited by racerabbit; 11-07-2009 at 03:14 PM..
Old 11-07-2009, 03:08 PM
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Get some red silicone orings that will fit in the double wall slip joint and stack some up in there and then slide the other pipe in on top of them.

Or get a large red silicone o'ring like the one that goes around the backplate on a K27 turbo. Cut it and feed it in the groove around and around. When you insert the pipe in there it will squeeze the orings down and seal the slip joint.

Another thing that should work if done well is red silicone high temp gasket sealer. Take the plastic nozzle that comes with a tube of that and cut a small hole in the end and squeeze a bunch of the red goo into the joint then put it together. that 'll take some time to squeeze enough in there to spread out and seal when you insert the pipe but it might work.
Old 11-07-2009, 03:38 PM
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OFF THE BOOST PIPE NOW...
 
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Muffler clamp...
Old 11-07-2009, 03:46 PM
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How are you noticing a leak at the slip joint?

Dose it sound like you have an exhaust leak at idle and or up until the waste gate opens?

Might also check the area at the Y going into the turbo. They like to crack there. At least mine did. If so, might check the turbo hot side. If a piece brakes off, it can chew up the turbine.

I would not expect that slip joint to leak enough to hear or make much of a difference in spool. Spool can also be lazy between shifts if the BOV/Compressor Bypass Valve function is not working as this can stall the turbo between shifts. Also, if the turbo is going-- it can get lazy. Been there and there to.
Old 11-07-2009, 04:23 PM
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SAIGON 68
 
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Teflon tape goes away at 350 degrees f.
Doesn't hi-temp silicone turn into fecal matter at 650 degrees f?
This slip is not that far from the exhaust valve.
0.8 bar. Do not assume accuracy of the gage. Even a new (generic automobile) gage. Just a thought....jp
Old 11-07-2009, 04:26 PM
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If you put a muffler clamp on there you'll lock up the joint and defeat the purpose of the slip joint to allow for engine expansion when hot.
Weld it or clamp it and the headers will possibly crack from the stress.

My B&B's leaked a tiny amount at the slip joint too. I didn't notice it unless I was under the car while it was running.
I squeeze some high temp red silicone in between the double walls of the slip joint before installing the headers to stop the leak.

I've seen inexpensive Schnell headers and they had a slip joint but it was not double wall.
Old 11-07-2009, 04:35 PM
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How about some header heat wrap insulation just around that point.
Old 11-07-2009, 05:01 PM
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I tried that first and it looked like crap and the next time I took the headers off it became dusty toxic trash.

Silicone in the slip joint works and you can't see it.
If you use quality red high temp silicone gasket sealer it won't burn up.

I've used a little smear of it to glue the metal exhaust port gaskets up in place so they don't slide down and fall off the exhaust studs (and they will) while you're under the car wrestleing with and installing the 2 halves of the B&B headers.
Old 11-07-2009, 05:15 PM
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The silicone holds up because it isn't exposed directly to the exhaust gasses, only the transferred temperature through the tubes. Silicone works, but isn't a permanent fix, it will probably need to be redone in a few years.
Old 11-07-2009, 05:29 PM
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OFF THE BOOST PIPE NOW...
 
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I was only kidding about the muffler clamp.

One you got it on, there would be no taking them apart easily.
Old 11-07-2009, 06:05 PM
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Crotchety Old Bastard
 
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Red silicon header gasket sealer.

Quote:
Silicone works, but isn't a permanent fix, it will probably need to be redone in a few years.
Most headers don't last more than a few years anyway so nothing to lose.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-07-2009, 06:59 PM
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